1. Field of the Invention
The present invention relates to a color liquid crystal device which provides a display by utilizing an electrooptic change generated between a pair of substrates having a plurality of electrodes constituting display element units, and, more particularly, to a color liquid crystal device which provides a display by utilizing an electrooptic change generated between a pair of substrates having a plurality of electrodes constituting display element units, and which has a color filter in its substrate. More specifically, the present invention concerns a color liquid crystal device which uses a color filter formed with a photosensitive precolored resin containing a coloring material at a regulated rate so as to eliminate defects in the orientation of liquid crystal molecules and provide a display of good quality.
2. Description of the Prior Art
Liquid crystal devices of the above-described type fall into two categories: a time division driven type of liquid crystal device (commonly known as a single matrix type) that consists of a pair of substrates having striped transparent electrodes formed perpendicular to those in another substrate and a twisted nematic type or ferroelectric liquid crystal material which is hermetically sealed between the substrates as an electrooptic modulation material, and an active matrix driven type of liquid crystal device (commonly known as an active matrix type) which have switching elements such as thin film transistors (commonly known as TFTs) for each display picture element.
In order to provide a color display, such liquid crystal devices must incorporate a transmission type color filter of red, green and blue on the surface thereof. In most cases, such color filters are disposed within the liquid crystal device in order to minimize the degree of parallax generated when the color display devices are viewed from the side.
Color filter incorporating liquid crystal devices of this type are in general formed by either of the following two methods:
In the first method, a color filter pattern 3 is formed on a substrate 1 on which a transparent electrode pattern 2 has been formed in such a manner as to be in alignment with the transparent electrode pattern 2, as shown in FIG. 4(a). If necessary, a protective layer 4 is formed over the entire surface, and an orientation film 5 is then formed on the protective layer 4. After a rubbing treatment has been conducted on the orientation film 5, the thus-formed first substrate is pasted with a second substrate, and a liquid crystal fluid is charged into the gap between the substrates so as to form a color liquid crystal device.
In the second method, the color filter pattern 3 is first formed on the substrate, as shown in FIG. 4(b), and the protective layer 4 is then formed over the entire surface, if necessary. After a transparent electrode layer made of a material such as Indium-Tin-Oxide is coated by sputtering or deposition and a photoresist pattern is applied to the transparent electrode layer 2, the transparent electrode layer 2 is selectively etched to form a transparent electrode pattern 2 in alignment with the color filter pattern. Subsequently, the photoresist pattern is removed, and the orientation film 5 is formed over the entire surface. After a rubbing treatment has been conducted to the orientation film 5, the thus-formed first substrate is pasted with a second substrate, and a liquid crystal fluid is charged into the gap between the substrates so as to form a color liquid crystal device.
In color filter incorporating liquid crystal devices of the above-described type, the performance of the liquid crystal device is greatly affected by the surface or side shapes of the color filter pattern and/or the properties of the color filter.
Conventionally, it has been known for a color filter to be formed with a precolored resin composed of a photosensitive resin containing a coloring material. Use of the photosensitive resin is advantageous because it can be formed into a fine pattern solely by use of the photolithographic process. The photosensitive resin is mixed with a coloring material beforehand to prepare a precolored resin, and the ratio at which they are mixed may induce problems involving the hardening of the resin and affecting the characteristics of the formed resin film.
For example, the mixture ratio may be a cause of problems relating to the patterning accuracy, such as peel-off of the resin owing to hardening failure and rough pattern edges or pattern surfaces, as well as cracks or breakage of the resin film that may occur in a subsequent process. The presence of any of these defects in the color filter may lead to a deflection in the orientation of the liquid crystal material, resulting in a color liquid crystal device which provides a poor display.